City-Scale, Building-Specific Load Factor and Contribution to a Utility’S Hour of Critical Generation
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Nailing the Peak: City-Scale, Building-Specific Load Factor and Contribution to a Utility’s Hour of Critical Generation Joshua R. New1,2,*, Mark B. Adams1, Eric Garrison2, William Copeland3, Brian Smith3, and Andy Campbell3 1Oak Ridge National Laboratory, Oak Ridge, TN, U.S.A. 2The University of Tennessee, Knoxville, TN, U.S.A. 3Electric Power Board, Chattanooga, TN, U.S.A. *Corresponding email: [email protected] Abstract difficult, time-varying aspect of energy use to reduce peak demand, typically defined by the utility’s hour of Maintaining electrical generation assets to meet peak maximum energy use each calendar month, the value of demand increases the cost of providing electricity to a time-varying energy efficiency [4] can be captured. country’s buildings and insufficient assets can result in Indeed, the growing ubiquity of smart, communication- power outages. In order to keep reliable electricity costs enabled devices has enabled energy use to be grid-aware low for consumers and demand charges low for utilities, and responsive through cost-effective sensing and control. there exist markets and financial incentives for limiting Energy efficiency (EE) and demand response (DR) may consumption during peak demand. or may not work together in buildings. Nemtzow’s The team has partnered with an electrical distributor decennial Green Effect meta-review of 100 DR programs 2 servicing a 1,390 km area and 178,368 buildings with the showed 20% EE gains to a 5% EE loss as a function of aim of using urban-scale building energy modelling to DR [5]. Other work shows an 8.8% peak cut with 13.3% inform business decisions necessary for the operation of increase in energy consumption for residential HVAC their electric grid. A suite of software has been developed equipment [6]. Preliminary results [7] from the authors’ that allows the scalable creation of a “digital twin” for all work seems to indicate EE gains can vary from -25% to buildings in the utility’s service area. This virtual utility +27% by building type as a function of a DR measure. area is analysed for targeted deployment of new technologies or policies to assess building-specific savings, effects on critically-loaded grid infrastructure Background (e.g. feeders, substations), and aggregated impact to The Electric Power Board of Chattanooga, TN (EPB) has utility-scale operations. deployed advanced metering infrastructure (AMI) and This work leverages 15-minute data from each building to securely shared 15-minute whole-building electrical compare actual and simulated monthly peak-hour demand consumption for over 150,000 buildings with Oak Ridge and assessment of the load factor for each building. National Laboratory (ORNL). EPB’s electrical Findings include market characterization via clustering of distribution network is backed by gigabit ethernet for relative energy use profiles for ~180,000 buildings as well utility-based smart grid operations [8], allowing it to as simulation-informed savings opportunities indicating function as a high-fidelity, utility-scale living laboratory residential load factors of 0.17, commercial load factors for EE and DR opportunities in the built environment. of 0.2-0.4 depending on year of construction, and general The partnership has enabled development of a suite of load factors of 0.16-0.5 depending on building type. software, referred to as Automatic Building detection and Energy Modeling (AutoBEM), that is: (1) able to collect Introduction cartographic, tax assessors, imagery (aerial- and street- level), elevation, and other data sources from multiple The U.S. Department of Energy has established resiliency locations; (2) process that data with computer vision, of critical infrastructure (i.e. the electric grid) as the top quality assurance, and related algorithms to extract priority for the Office of Electricity with a synergistic building-specific features; (3) automatically combine Grid-interactive Efficient Buildings (GEB) initiative [1] those features to create OpenStudio and EnergyPlus by the Building Technologies Office which extends building energy models of each building; (4) quickly energy efficiency of buildings to understanding time-of- simulate each building for large geographical areas on use grid impacts. world-class high performance computing resources; (5) As buildings become more energy efficient and with the modify buildings and compare results to show impacts of increasing proliferation of decentralized renewable new technologies or policies in terms of energy, demand, generation, many utilities are seeing an erosion of revenue emissions, and cost; and (6) aggregate, summarize, and per customer and actively looking to evolve the traditional interactively visualize the results for any area in a way that utility business model. The challenge of balancing scales from building-specific, 15-minute impacts to regulatory requirements between supply and demand is critically-loaded infrastructure, to the entire electrical becoming more difficult and costly as indicated by the distribution grid. This “virtual utility” of all buildings in trend of the “duck curve” [2][3]. By capturing the more the service area allows city-scale, building-specific analysis with low-cost, same-day turnaround for most Our team first selected time periods of interest (e.g. what-if scenarios. business hours on weekdays) to time-bin the electricity Relevant prior work includes survey and comparison use for all buildings. We then identify relative usage matrix of 37 different building-specific data sources [9], patterns by applying standard normalization, resulting in microclimate variation of energy use [10], urban-scale each building’s peak 15-minute use value as 1.0 and its energy modelling capabilities [11]-[15], long-term lowest as 0.0. climate and resiliency [16][17], creation and analysis of a virtual utility [18], and assessment of BEM accuracy to actual 15-minute energy use from over 150,000 real buildings [19]. This “digital twin” of a utility has leveraged over 3 million simulations and 13TB of data to quantify $11-35 million in savings across 9 scenarios that may be operationally refined, validated, and shared via case studies for consideration by other utilities. These 9 monetization scenarios fall under 5 use cases related to potential changes in rate structure, demand side management, emissions, energy efficiency, and comparative analysis for customers’ consumption [18]. Figure 2. A plot of 24-hour energy use for two actual buildings’ Once a robust software Measure is written, the current 15-minute profiles shows similar trends that might indicate system requires under 7 hours to modify every building candidacy for a specific DR technology. model, perform an annual simulation, visualize cost savings (see Figure 1) using wholesale or retail rate Clustering, via k-means, was used to segment all classes, analyze/aggregate electrical load changes to customers into significantly different load-shape patterns areas-of-interest, and store relevant data in the utility’s by minimizing the distance from each observation to the operational business intelligence systems. k cluster centroids based on within-cluster sum squared difference by adjusted/normalized kWh as defined by Equation 1 (1) where μi is the mean of the observations, x, assigned to cluster Si. By clustering buildings into unique load shapes, it is anticipated that additional building characteristics relevant to marketing and niche DR applications might be made known. Analysis of simulated building energy data EnergyPlus [20] and OpenStudio [21] are the building physics simulation engine and middleware software development kit in which DOE has invested $93 million since 1995. New features, better runtime performance, Figure 1. Utility-scale, building-specific impact can be assessed and creation of new prototype models of building types for energy, demand, emissions, and cost impacts by leveraging have recently been created from assessments of real big data collection, HPC-enabled processing, simulation of buildings [22][23] to facilitate accurate and timely each building, and interactive visual analytics. modeling of the U.S. building stock. We leverage these tools to create and simulate models of every building in Methods the utility’s service area where, due to privacy concerns, Clustering of actual building energy data there are no internal details of the buildings directly Utilities are more frequently formalizing analysis related sensed. to higher-resolution AMI data. Shown in Figure 2 is an Quality assurance and quality control methods were example of 2 buildings’ scaled kilowatt-hour (kWh) previously applied to the actual 15-minute AMI data [19]. energy pattern from midnight to midnight with data points The actual annual 15-minute energy use intensity (EUI), for every 15 minutes. While a similar pattern is observed, kWh per building floor area, was stored in a ~35,040- common utility questions may include: (1) “how would element long feature vector for every building. Each we effectively visualize all customers’ data for a year?” building’s actual profile vector was then compared and (2) “how can we show which customers are similar in against the simulated data for 3 residential vintages and a way that is useful?” every combination of the 6 vintages of 16 commercial building types using a dynamic 35,040-dimensional was able to identify unique usage patterns that are Euclidean distance. actionable. As shown in the top row of Figure 3, our team A common metric used by utilities is “load factor,” which was able to identify a typical residential trend with peaks is the ratio of the average energy use to peak demand as between 5:00 and 7:00pm. This type of average daily defined in equation 2. If a building’s site DR was perfectly profile from 15-minute data can help utilities identify the managed, its energy use would not vary with time and highest peak-hour contributors. Indeed, the 26,048 yield a load factor of 1. Conversely, a building with a load residential meters belonging to the cluster shown in the factor near 0 may have significant opportunities for DR.